Experiments will be conducted to determine the effects of nutritional factors, hormones, and drugs on insulin biosynthesis. Synthesis and turnover of pancreatic proinsulin and insulin will be measured in vivo by injecting labelled amino acids and purifying the radioactive hormones by affinity chromatography. The rate of synthesis and turnover will be determined from the rate of change of the specific activities of the hormones with time. Control of insulin biosynthesis in isolated Islets of Langerhans will be studied at the transcriptional and post-transcriptional level. The size of proinsulin messenger RNA will be estimated. A cell free protein synthesizing system will be used to assay proinsulin mRNA extracted from fish islets and hamster insulinomas. To determine how glucose stimulates proinsulin synthesis relative to total islet protein synthesis in the absence of new RNA synthesis, measurement of the synthesis time of islet proteins compared to proinsulin synthesis time and rates of initiation of islet protein synthesis will be determined. The overall objective is to determine how glucose alters proinsulin mRNA metabolism, and how this mRNA is selectively translated.